/*
   +----------------------------------------------------------------------+
   | PHP Version 5                                                        |
   +----------------------------------------------------------------------+
   | Copyright (c) 1997-2013 The PHP Group                                |
   +----------------------------------------------------------------------+
   | This source file is subject to version 3.01 of the PHP license,      |
   | that is bundled with this package in the file LICENSE, and is        |
   | available through the world-wide-web at the following url:           |
   | http://www.php.net/license/3_01.txt                                  |
   | If you did not receive a copy of the PHP license and are unable to   |
   | obtain it through the world-wide-web, please send a note to          |
   | license@php.net so we can mail you a copy immediately.               |
   +----------------------------------------------------------------------+
   | Author: Sascha Schumann <sascha@schumann.cx>                         |
   +----------------------------------------------------------------------+
*/

/* $Id$ */

#include "php.h"
#include "php_lcg.h"

#include <folly/portability/SysTime.h>
#include <folly/portability/Unistd.h>

#ifdef ZTS
int lcg_globals_id;
#else
static php_lcg_globals lcg_globals;
#endif

#ifdef PHP_WIN32
#include <process.h>
#endif

static void lcg_seed(TSRMLS_D);

/*
 * combinedLCG() returns a pseudo random number in the range of (0, 1).
 * The function combines two CGs with periods of
 * 2^31 - 85 and 2^31 - 249. The period of this function
 * is equal to the product of both primes.
 */

#define MODMULT(a, b, c, m, s) q = s/a;s=b*(s-a*q)-c*q;if(s<0)s+=m

PHPAPI double php_combined_lcg(TSRMLS_D) /* {{{ */
{
  php_int32 q;
  php_int32 z;

  if (!LCG(seeded)) {
    lcg_seed(TSRMLS_C);
  }

  MODMULT(53668, 40014, 12211, 2147483563L, LCG(s1));
  MODMULT(52774, 40692, 3791, 2147483399L, LCG(s2));

  z = LCG(s1) - LCG(s2);
  if (z < 1) {
    z += 2147483562;
  }

  return z * 4.656613e-10;
}

static void lcg_seed(TSRMLS_D) /* {{{ */
{
  struct timeval tv;

  if (gettimeofday(&tv, NULL) == 0) {
    LCG(s1) = tv.tv_sec ^ (tv.tv_usec<<11);
  } else {
    LCG(s1) = 1;
  }
#ifdef ZTS
#ifdef _MSC_VER
  LCG(s2) = (long)pthread_getw32threadid_np(pthread_self());
#else
  LCG(s2) = (long) tsrm_thread_id();
#endif
#else
  LCG(s2) = (long) getpid();
#endif

  /* Add entropy to s2 by calling gettimeofday() again */
  if (gettimeofday(&tv, NULL) == 0) {
    LCG(s2) ^= (tv.tv_usec<<11);
  }

  LCG(seeded) = 1;
}
/* }}} */

static void lcg_init_globals(php_lcg_globals *lcg_globals_p TSRMLS_DC) /* {{{ */
{
  LCG(seeded) = 0;
}
/* }}} */

PHP_MINIT_FUNCTION(lcg) /* {{{ */
{
#ifdef ZTS
  ts_allocate_id(&lcg_globals_id, sizeof(php_lcg_globals), (ts_allocate_ctor) lcg_init_globals, NULL);
#else
  lcg_init_globals(&lcg_globals);
#endif
  return SUCCESS;
}
/* }}} */
